The history of luaTEX 2006–2009 / v 0.50 - Pragma ADE

In LuaTEX with ConTEXt MkIV support for traditional Type1 fonts is also simplied: only the
pfb and afm les are needed. Currently we only need tfm les for math fonts but that
will change too. Virtual fonts can be built at runtime and we are experimenting with real
time font generation. Of course lenames are still just as messy and inconsistent as ever,
so other tools are still needed to gure out the real names of fonts.
So, what is this OpenType and will it really make TEXies life easier? The qualication ‘open’
in OpenType carries several suggestions:
• the format is dened in an open way, everybody can read the specication and what
is said there is clear
• the format is open in the sense that one can add additional features, so there are no
limits and/or limits can be shifted
• there is an open community responsible for the advance of this specication and
commercial objectives don't interfere and/or lead to conicts
Is this true or not? Indeed the format is dened in the open although the formal specication
is an expensive document. A free variant is available at the Microsoft website but
it takes some effort to turn that into a nicely printable document. What is said there is
quite certainly clear for the developers, but it takes quite some efforts to get the picture.
The format is binary so one cannot look into the le and see what happens.
The key concept is ‘features’, which boils down to a collection of manipulations of the text
stream based on rules laid down in the font. These can be simple rules, like ‘replace this
character by its smallcaps variant’ or more complex, like ‘if this character is followed by
that character, replace both by yet another’. There are currently two classes of features:
substitutions and (relative) positioning. One can indeed add features so there seem to
be no limits.
The specication is a hybrid of technologies developed by Microsoft and Adobe with
some inuence by Apple. These companies may have conicting interests and therefore
this may inuence the openness.
So, in practice we're dealing with a semi-open format, crippled by a lack of documentation
and mostly controlled by some large companies. These characteristics make that
developing support for OpenType is not that trivial. Maybe we should keep in mind that
this font format is used for word processors (no focus on typography), desk top publishing
(which permits in-situ tweaking) and rendering text in graphical user interfaces (where
script and language specic rendering is more important than glyph variants). Depending
on the use features can be ignored, or applied selectively, of even compensated.
Anyhow, a font specication is only part of the picture. In order to render it useful we
need support in programs that display and typeset text and of course we need fonts. And
in order to make fonts, we need programs dedicated to that task too.
224 OpenType: too open?